With the recent changes in industrial structure and working environment, the amount of toxic chemicals being used is on the increase. Accordingly, the issues on the manufacture, use, and treatment of waste chemicals have been raised, and human bodies are now exposed to environments where chemicals are present not only in the working sites but also via various routes. Nevertheless, the development of protective clothes which can detect the changes in working environment according to the use of toxic chemicals is far from satisfaction.
As such, attempts were made to prepare protective clothes by applying pH-detecting chromic dyes, however, the conventional pH-detecting chromic dyes had problems in that they could not be dyed into fibers, and that, even they were dyed, the chromic action of colors according to pH change disappeared in the dyed state. Additionally, the chromic dyes had a problem in that they were discolored and faded by laundering, sunlight, etc., thus are not usable.
Therefore, attempts have been made to develop a novel dye for acid detection, and a previous reference (Acta Crystallographica Section C Crystal structure Communications, 2009, 65 (10), 543-548) discloses that 4-(phenyldiazenyl)aniline reacts with 5-sulfosalicylic acid or benzenesulfonic acid to form a proton-transfer red-black dye and that 4-(phenyldiazenyl)aniline forms a 1:2 non-transfer complex compound with 3,5-dinitrobenzoic acid. However, these structures only describe the color changes by the binding with a particular acidic compound, and they cannot be considered to have characteristics for pH-detection.
Meanwhile, hydrofluoric acid is an aqueous solution of hydrofluoride (HF) and a colorless pungent liquid, which fumes in the air, is toxic and has small surface tension and strong penetration ability, and thus can strongly penetrate into the skin or the mucus. Therefore it requires special attention for its handling. Hydrofluoric acid has good reactivity, and reacts with oxides of metals such as alkali, alkali earth metal, lead, zinc, silver, etc., hydroxides, or carbonates thereby forming fluorides. In plating, hydrofluoric acid is used in a plating bath for tin, lead, solder, chromium, etc., as a fluoride bath. Additionally, hydrofluoric acid is also used for corrosion of glass, sand removal of the casting, treatment of stainless steel surface, pre-treatment of plating, etc.
Currently, companies which use hydrofluoric acid are equipped with accident prevention system by installing a gas leak alarm device against the leakage of hydrofluoric acid, and additionally, infrared cameras or CCTVs are installed for use. The gas leak alarm device serves to detect a combustible gas or a gas with toxic materials, reveals the concentrations of these gases, and automatically alarms in their preset gas concentrations. However, the gas leak alarm device does not alarm until the gases reach a certain concentration or higher, and thus the gas leak alarm device was not sufficient for immediate response for on-site workers. Furthermore, the gas leak alarm device also becomes a cause for serious accidents due to its malfunction.
In this regard, there is an urgent need for the development of protective clothes which help workers to easily detect acid in work sites and actively recognize dangerous situation thereby preventing the damages from safety accidents and secondary accidents.
For the development of protective clothes which can help workers to actively recognize the harmful situation of strong acid thereby preventing the workers from the damages of safety accidents and secondary accidents, the present inventors have endeavored to develop a dye, which changes its color when exposed to an acidic material and maintains its characteristics even after it is dyed into a fiber. As a result, they have discovered that when a fiber was dyed using the N,N-dialkylaniline azobenzene, the resulting fiber showed a color change to a trace amount of acidic material and also showed high color fastness when dyeing, thereby completing the present invention.